News Column

Patent Issued for Liquid Crystal Display Device

June 24, 2014



By a News Reporter-Staff News Editor at China Weekly News -- Japan Display Inc. (Tokyo, JP) has been issued patent number 8749731, according to news reporting originating out of Alexandria, Virginia, by VerticalNews editors.

The patent's inventors are Oshima, Tetsuya (Mobara, JP); Imayama, Hirotaka (Mobara, JP); Shiraishi, Yasuhisa (Mobara, JP); Nagae, Yoshiharu (Hitachi, JP).

This patent was filed on May 22, 2013 and was published online on June 10, 2014.

From the background information supplied by the inventors, news correspondents obtained the following quote: "The present invention relates to a liquid crystal display device, and more particularly to a liquid crystal display device which includes a backlight.

"A liquid crystal display panel is configured such that an envelope is formed of a pair of substrates which sandwiches liquid crystal therebetween, and optical transmissivity of the liquid crystal display panel is controlled over a plurality of pixels which are formed in the spreading direction of the liquid crystal. Accordingly, a liquid crystal display device is usually provided with a backlight which is a planar light source on a surface (back surface) of the liquid crystal display panel on a side opposite to a viewer.

"Such a liquid crystal display device is configured to radiate light from the backlight through the liquid crystal display panel with a relatively large angle with respect to a perpendicular of the liquid crystal display panel. That is, the liquid crystal display device is a liquid crystal display device having a so-called wide viewing angle characteristic which allows a plurality of viewers to observe an image on the liquid crystal display panel simultaneously.

"On the other hand, however, there has been also a demand that, for example, only a viewer himself is allowed to observe an image on the liquid crystal display panel. For example, as disclosed in JP-A-1994-59287, there has been known a liquid crystal display device which can adjust a viewing angle state from a wide viewing angle state to a narrow viewing angle state.

"The liquid crystal display device disclosed in JP-A-1994-59287 is configured such that a guest-host liquid crystal cell is arranged between a backlight and a liquid crystal display panel and hence, when the guest-host liquid crystal cell is driven, light from the backlight can be radiated with a small angle with respect to a perpendicular of the liquid crystal display panel. The guest-host cell per se can adjust a viewing angle of light which passes through the guest-host liquid cell."

Supplementing the background information on this patent, VerticalNews reporters also obtained the inventors' summary information for this patent: "However, the liquid crystal display device disclosed in JP-A-1994-59287 is configured such that the guest-host liquid crystal cell having a relatively large thickness is interposed between the liquid crystal display panel and the backlight. Accordingly, there arises a drawback that a thickness of the liquid crystal display device is largely increased. Further, the guest-host liquid crystal cell has the relatively complicated configuration thus giving rise to a drawback that a manufacturing cost of the liquid crystal display device is pushed up. Further, the adjustment of a viewing angle of the guest-host liquid crystal cell is performed by applying a voltage to the guest-host liquid crystal cell and hence, there arises a drawback that the increase of power consumption is unavoidable.

"It is an object of the invention to provide a liquid crystal display device which can adjust a viewing angle with the simple configuration without incurring the large increase of a thickness and the increase of power consumption.

"The liquid crystal display device of the invention is configured such that, for example, two prism sheets are arranged between a liquid crystal display panel and a light guide plate in an overlapping manner, and the prism sheet on a liquid-crystal-display-panel side (first prism sheet) is displaced thus performing a control on whether light which is radiated from the light guide plate and is incident through the prism sheet on a light-guide-plate side (second prism sheet) is allowed to be reflected on the first prism sheet or to pass through the first prism sheet directly so as to adjust a viewing angle.

"Further, the liquid crystal display device of the invention may use one prism sheet corresponding to the first prism sheet in place of two prism sheets and may make the light guide plate also play a role of the second prism sheet.

"The liquid crystal display device of the invention can be configured as follows, for example.

"(1) According to one aspect of the invention, there is provided a liquid crystal display device which includes: a liquid crystal display panel; and a backlight which is arranged on a back surface of the liquid crystal display panel, wherein

"the backlight includes a light source, a light guide plate, a first prism sheet which is arranged between the liquid crystal display panel and the light guide plate, and a second prism sheet which is arranged between the first prism sheet and the light guide plate,

"the first prism sheet includes first prisms which are formed parallel to each other in the first direction on a liquid-crystal-display-panel-side surface thereof,

"the first prism formed on the first prism sheet includes a first inclined surface and a second inclined surface which respectively extend in the second direction which intersects the first direction,

"assuming light which is emitted from the light source, enters the light guide plate through a side surface of the light guide plate, and is radiated from an upper surface of the light guide plate as a first light, and light which enters the light guide plate through the upper surface of the light guide plate and is radiated from the upper surface of the light guide plate as a second light,

"the second prism sheet includes second prisms which convert the first light into a third light whose light quantity has the distribution where a magnitude of light quantity is periodically changed at a pitch of the first prisms formed on the first prism sheet in the first direction and allow the third light to be incident on the first prism sheet,

"the first prism sheet, upon impingement of the third light on the first inclined surfaces, reflects the third light toward a second-inclined-surface side on the first inclined surfaces thus reflecting at least a portion of the third light toward a light-guide-plate side on the second inclined surface,

"the first prism sheet, upon impingement of the third light on the second inclined surfaces without via the first inclined surfaces, radiates the third light toward a liquid-crystal-display-panel side, and

"the first prism sheet is displaceable between a first state in a wide viewing angle mode where a rate that the third light impinges on the second inclined surfaces without via the first inclined surfaces is smaller than a rate that the third light impinges on the first inclined surface and a second state in a narrow viewing angle where the rate that the third light impinges on the second inclined surfaces without via the first inclined surfaces is larger than the rate that the third light impinges on the first inclined surface.

"(2) In the liquid crystal display device having the configuration (1), the displacement of the first prism sheet may be performed in the first direction.

"(3) In the liquid crystal display device having the configuration (1), the displacement of the first prism sheet may be performed in the direction perpendicular to a main surface of the first prism sheet.

"(4) In the liquid crystal display device having the configuration (1), the plurality of second prisms which are formed parallel to each other in the first direction may be formed on a first-prism-sheet-side surface of the second prism sheet,

"the second prism formed on the second prism sheet may include a third inclined surface and a fourth inclined surface which respectively extend in the second direction, and

"the third light may be radiated from the fourth inclined surfaces.

"(5) In the liquid crystal display device having the configuration (1), the second light may be a diffused light.

"(6) In the liquid crystal display device having the configuration (1), the liquid crystal display panel may include a pair of substrates which sandwiches liquid crystal therebetween, and the liquid crystal may be driven by an electric field which has components parallel to the pair of substrates.

"(7) According to another aspect of the invention, there is provided a liquid crystal display device which includes: a liquid crystal display panel; and a backlight which is arranged on a back surface of the liquid crystal display panel, wherein

"the backlight includes a light source, a light guide plate, a prism sheet which is arranged between the liquid crystal display panel and the light guide plate,

"the prism sheet includes first prisms which are formed parallel to each other in the first direction on a liquid-crystal-display-panel-side surface thereof,

"the first prism formed on the prism sheet includes a first inclined surface and a second inclined surface which respectively extend in the second direction which intersects the first direction,

"assuming light which is emitted from the light source, enters the light guide plate through a side surface of the light guide plate, and is radiated from an upper surface of the light guide plate as a first light, and light which enters the light guide plate through the upper surface of the light guide plate and is radiated from the upper surface of the light guide plate as a second light,

"the light guide plate includes, on a lower surface thereof, second prisms which radiate the first light from an upper surface of the light guide plate such that the first light turns into a light whose light quantity has the distribution where a magnitude of light quantity is periodically changed at a pitch of the first prisms formed on the prism sheet in the first direction,

"the prism sheet, upon impingement of the first light on the first inclined surfaces, reflects the first light toward a second-inclined-surface side on the first inclined surfaces and reflects at least a portion of the first light toward a light-guide-plate side on the second inclined surface,

"the prism sheet, upon impingement of the first light on the second inclined surfaces without via the first inclined surfaces, radiates the first light toward a liquid-crystal-display-panel side, and

"the prism sheet is displaceable between a first state in a wide viewing angle mode where a rate that the first light impinges on the second inclined surfaces without via the first inclined surfaces is smaller than a rate that the first light impinges on the first inclined surface and a second state in a narrow viewing angle mode where the rate that the first light impinges on the second inclined surfaces without via the first inclined surfaces is larger than the rate that the first light impinges on the first inclined surface.

"(8) In the liquid crystal display device having the configuration (7), the displacement of the prism sheet may be performed in the first direction.

"(9) In the liquid crystal display device having the configuration (7), the displacement of the prism sheet may be performed in the direction perpendicular to a main surface of the prism sheet.

"(10) In the liquid crystal display device having the configuration (7), a pitch of the second prisms may be equal to a pitch of the first prisms.

"(11) In the liquid crystal display device having the configuration (7), the second light may be a diffused light.

"(12) In the liquid crystal display device having the configuration (7), the liquid crystal display panel includes a pair of substrates which sandwiches liquid crystal therebetween, and the liquid crystal is driven by an electric field which has components parallel to the pair of substrates.

"(13) According to still another aspect of the invention, there is provided a liquid crystal display device which includes: a liquid crystal display panel; and a backlight which is arranged on a back surface of the liquid crystal display panel, wherein the backlight includes a plurality of optical sheets, and at least one optical sheet is displaced so as to adjust a viewing angle.

"(14) According to still another aspect of the invention, there is provided a liquid crystal display device which includes: a liquid crystal display panel; and a backlight which is arranged on a back surface of the liquid crystal display panel, wherein the backlight includes a plurality of optical sheets, and at least one optical sheet is moved so as to adjust a viewing angle.

"(15) In the liquid crystal display device having the configuration (13), the plurality of optical sheets may be formed of a prism sheet respectively.

"(16) In the liquid crystal display device having the configuration (14), the plurality of optical sheets may be formed of a prism sheet respectively.

"(17) In the liquid crystal display device having the configuration (13), the displacement may be performed in the horizontal direction.

"(18) In the liquid crystal display device having the configuration (13), the displacement may be performed in the vertical direction.

"(19) In the liquid crystal display device having the configuration (14), the movement may be performed in the horizontal direction.

"(20) In the liquid crystal display device having the configuration (14), the movement may be performed in the vertical direction.

"The above-mentioned configurations are merely examples, and the invention can be suitably modified without departing from the technical concept of the invention. Further, configurational examples of the invention other than the above-mentioned configurational examples will become apparent from the description of the whole specification and attached drawings.

"The liquid crystal display device having the above-mentioned configurations can adjust a viewing angle in spite of the simple configuration thereof.

"Other advantageous effects of the invention will become apparent from the description of the whole specification."

For the URL and additional information on this patent, see: Oshima, Tetsuya; Imayama, Hirotaka; Shiraishi, Yasuhisa; Nagae, Yoshiharu. Liquid Crystal Display Device. U.S. Patent Number 8749731, filed May 22, 2013, and published online on June 10, 2014. Patent URL: http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO1&Sect2=HITOFF&d=PALL&p=1&u=%2Fnetahtml%2FPTO%2Fsrchnum.htm&r=1&f=G&l=50&s1=8749731.PN.&OS=PN/8749731RS=PN/8749731

Keywords for this news article include: Asia, Japan Display Inc.

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Source: China Weekly News


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